Apparatus for cooling a piston



April 67 D. TILLACK 3,314,402

Filed June 5, 1965 5 Sheets-Sheet 2 INVENTOR. DIETRICH TILLACK Bfnde amol HTTORNEYS April 18, 1967 D. TILLACK 3,314,402

Filed June 5, 1965 5 Sheets-Sheet 5 INVENTO DIETRICH TILL April 18, 1967 v i TILLACK 3,314,402

APPARATUS FOR COOLING A PISTON Filed June 5, 1965 5 Sheets-Sheet 4 as. Y,

28d r m INVENTOR. DIET-RICH TILLACK April 18, 1967 TlLLAcK 3,314,402

APPARATUS FOR 000mm A PISTON Filed June 5, 1965 5 sheets-Sheet 5 FIG. 8 F569 FIG. IO

FIG. FIG. i2

. INVENTO DIETRICH TILLACK FIG. l3 G Xw w United States Patent O 3,314,402 APPARATUS FOR COOLING A PISTON Dietrich Tillack, Rostock, Germany, assignor to Veb Dieselmotorenwerk Rostock, Rostock, Germany Filed June 3, 1965, Ser. No. 460,972 12 Claims. (Cl. 123-41.35)

The present invention relates to pistons of internal combustion engines and in particular to pistons which are provided with structure by which they are cooled.

In particular, the invention relates to pistons which are subjected to high operating temperatures likely to cause carbon deposits from the cooling oil, so that the structure for distributing the cooling oil, particularly along the interior of the piston, becomes very important and should be capable of preventing the build up of any deposits inside the piston.

It is known to conduct heat away from the interior of a hollow piston of an internal combustion engine, particularly at those parts of the piston which are subjected to relatively high temperatures, by use of the most Widely differing structures. There are structures which positively spray the interior surfaces of the piston, the cooling fluid being transmitted under pressure through a passage in the connecting rod and being directed in a free spray against the inner transverse surface of the hollow piston. This type of cooling structure does not, however, guarantee a sufliciently good removal of heat from engines which operate at high temperatures, since a large part of the cooling oil drops off the inner surface of the piston without having received any substantial amount of heat.

With other types of piston cooling structures the stream of cooling liquid is directed along predetermined paths through inserts which are fixed directly within the piston. However, these inserts are of considerable disadvantage since they do not sufficiently prevent carbon deposits from the cooling liquid and since the passages of the inserts become clogged, so that they must be cleaned from time to time at a not inconsidera'ble expense. Otherwise, because of the reduction in heat transfer within the clogged passages, the increase in temperature in the piston during operation thereof will result in suflicient deformation of the piston to cause seizing as well as cracking in the end wall of the piston and in its cylindrical part.

Another type of known structure involves directing the oil against the inner transverse surface of the piston by way of an extension of the connecting rod which is pressed against the inner surface of the piston either by a spring or by the oil pressure, this member which engages the inner transverse surface of the piston having a mushroom-shaped configuration and swinging back and forth so as to wipe across a part of the interior transverse surface of the hollow piston against which an oil film is maintained. This construction also is of considerable disadvantage, however, because of the different degrees of heat transfer setting up undesirable stresses in the piston. Thus, at the area where the wiper member slides across the interior surface of the piston there is quite a good heat transfer, and this surface of the piston is maintained quite clean at all times. However, the parts of the inner surface of the piston which are not engaged by the mushroom-shaped, swinging wiper member receive carbon deposits as if there were no particular cooling structure, and thus the heat transfer at these latter parts of the piston is considerably less than the parts which are maintained clean, so that this differential in transfer of heat away from the piston creates undesirably large stresses therein.

It is to be noted that the interior of the hollow piston has at its innermost end a transverse surface and the 3,314,402 Patented Apr. 18,1967

piston also has an inner cylindrical surface extending from the inner transverse surface, and it is important to cool this latter cylindrical surface, at least in the region of the inner transverse surface, particularly since this is the part of the piston which at its exterior carries the piston rings. A device of the above type cannot perform any cooling function with respect to the inner cylindrical piston surface at the region surrounded by the piston rings. Proper cooling at this part of the piston is of the utmost importance inasmuch as the temperature of the uppermost groove of the piston which receive the uppermost ring should not exceed 200 C. In order to prevent the lubricating oil, which is in the groove which receives the uppermost piston ring, from depositing undesirable residues which would result in improper operation of the piston ring. The uppermost piston ring will operate properly only if the temperature in the groove which receives it is less than 200 C. Of course, a device of the above type, where a mushroom-shaped wiper member swings back and forth across a surface, is necessarily limited to a reciprocating type of piston which is driven through a swinging connecting rod. A piston which has a fixed coaxial piston rod, such as a piston of the type used in a crosshead engine, could not be cooled with such a structure. Also, a structure of this latter type cannot be built symmetrically about the axis of the piston, and this factor also contributes to undesirable creation of heat stresses and deformation of the piston.

It is accordingly a primary object of the present invention to provide a piston with a cooling structure capable of reliably cooling the interior surface of the piston all the way across the innermost transverse surface portion thereof as well as along the inner cylindrical surface portion at its region adjoining the inner transverse surface of the piston.

Also, it is an object of the present invention to provide a structure of this type which can be used with all types of relatively large engines.

In particular, it is an object of the invention to provide for a piston a structure which will very reliably distribute the cooling oil along the interior surface of the piston so as to provide proper cooling thereof.

Moreover, it is an object of the invention to provide a structure which will create a considerable turbulence in the cooling fluid so as to intensify the cooling action.

In addition, it is an object of the invention to provide a structure which is quite simple to assemble and manufacture, which does not undesirably increase the weight of the piston, and which is also symmetrical with respect to the axis of the piston.

Primarily with the structure of the invention the piston carries at its interior a support means which serves to support a rotary means of the invention between the support means and the inner transverse surface of the piston. This rotary means itself has a transverse surface which is directed toward the transverse surface of the piston, and a fluid guide means is fixed to and projects from the transverse surface of the rotary means toward the transverse surface of the piston, this fluid guide means being formed by suitably shaped ribs or the like which are fixed to the rotary means for rotary movement therewith. A conduit means communicates with the space between the inner transverse piston surface and the transverse surface Oif the rotary means from which the fluid guide means projects, so that through this conduit means the cooling oil under pressure can be delivered to the fluid guide means and the oil under pressure itself acts on the fluid guide means to rotate the rotary means which thus turns the fluid guide means so as to distribute the cooling oil during rotation of the rotary means. In this way undesirable deposits are reliably avoided and a highly efficient cooling action can be maintained.

The invention is illustrated by way of example in the accompanying dawings which form part of the application and in which:

FIG. 1 is a sectional elevation of one embodiment of a structure according to the present invention;

' FIG. 2 is a sectional plan view of the structure of FIG. 1 taken along line 22 of FIG. 1 in the direction of the arrows;

FIG. 3 is a sectional elevation of another embodiment of a structure according to the invention;

FIG. 4 is a sectional plan of the structure of FIG. 3 taken along line 44 of FIG. 3 in the direction of the arrows;

FIG. 5 is a sectional elevation of a third embodiment of a structure according to the present invention;

FIG. 6 is a transverse section taken along lines 66 of FIG. 5 in the direction of the arrows;

FIG. 7 is a sectional elevation of yet another embodiment of a structure according to the present invention;

FIG. 8 is a fragmentary sectional view on an enlarged scale, as compared to FIGS. 1-7, showing part of the transverse end wall of the piston and the rotary member therein, the plane of FIG. 8 being the same sectional plane as that of FIGS. 1, 3, 5, and 7;

FIG. 9 is a fragmentary transverse section of the struc ture of FIG. 8 taken along line 9-9 of FIG. 8 in the direction of the arrows;

FIG. 10 is a fragmentary sectional view of the same region of the structure as that illustrated in FIG. 8 but showing a different embodiment of the structure;

FIG. 11 is also a sectional view of the same region of the assembly as that illustrated in FIG. 8 but showing a different embodiment;

FIG. 12 is a transverse section of the structure of FIG. 11 taken along line 12-12 of FIG. 11 in the direction of the arrows;

FIG. 13 is a sectional illustration of another embodiment of a structure which may be used at the same region as that illustrated at FIG. 8;

FIG. 14 is a transverse section of the structure of FIG. 13 taken along line 14-14 of FIG. 13 in the direction of the arrows;

FIG. 15 is yet another embodiment of a structure shown on anenlarged scale and taken in the same plane as that of FIGS. 1, 3, 5 and 7, the structure of FIG. 15 also being used at the same region as that illustrated in FIG. 8;

FIG. 16 is a fragmentary sectional view of still another embodiment of a structure which is used between the inner surface of the piston and a rotary means which cooperates therewith, the region of FIG. 16 being the same as that of FIG. 8; and

FIG. 17 is a transverse section taken along line 17-17 of FIG. 16 in the direction of the arrows.

Referring to FIG. 1, the piston 1a is itself of a conventional construction and has a hollow interior, as indicated in FIG. 1. Along the hollow interior of the piston 1a extends a conduit 2a through which oil under pressure is directed to the innermost part of the hollow interior of the piston 1a in order to cool the piston, this oil being supplied along the conduit 2a in a manner well known in the art and forming no part of the present invention. The piston 1a includes in its interior an inner transverse surface 25a from which a cylindrical inner surface 26a extends in the region of the surface 25:: and in the region surrounded by the piston rings which are received in the grooves 27a, and it is to the surface 25a that the cooling oil is directed by the conduit The piston 1a fixedly carries in its hollow interior a support means 3a in the form of a hollow rigid body of a suitable annular bearing 4a. Thus, the uppermost surface of the support 3a is formedwith an annular shoulder into which the bearing ring 4a extends, and this bearing ring in turn supports for rotation a plate which is fixed to the hollow interior of the rotary body 5a which, it will be noted, itself has a transverse surface 28a spaced from and directed toward the transverse surface 25a of the piston 1a. Thus, it will be seen that the bearing plate 29a is fixed by suitable screws to the underside of the hollow rotary means 5a, and this hollow rotary means 5a is provided at its outer periphery with a downwardly extending cylindrical portion 30a which extends along the uppermost part of the cylindrical surface 26a.

Between the surfaces 25a and 28a, which define a predetermined space between themselves, is situated the fluidguide means 6 shown most clearly in FIG. 2. This fluidguide means takes the form of rib-like projections having the configuration indicated in FIG. 2 and fixed integrally with the rotary means 5a and projecting therefrom to the surface 25a from which they may be spaced only by a clearance sufficient to maintain a film of oil against the surface 25a. These fluid-guiding ribs curve from the surface 28a downwardly along the portion 30a of the rotary means 5a so as to extend along surface 26a also. As may be seen from FIG. 2, the fluid-guide means 6 includes one set of fluid guiding elements 61a which extend all the way to the central opening 52 through which the oil reaches the space between the surfaces 25a and 28a and through which the oil has access to the surface 251: to flow therefrom to the surface 26a, as indicated by the arrows in FIG. 1. The other set of ribs 61b alternate with the ribs 61a and terminate short of the opening 52, as is apparent from FIG. 2.

The conduit means includes, in addition to the supply conduit 2a, a return flow conduit 7a which communicates wit-h the space surrounding the support 3a in the manner shown at the left part of FIG. 1. Thus, the oil which issues from the conduit 2a through the opening 52 into the space between the transverse surfaces 25a and 280 will flow in the manner indicated by the arrows in FIG. 1 across the space between the surfaces 25a and 28a and then downwardly along the skirt portion 30a of the rotary means 50 so as to cool the surface 26a also, and then the oil reaches the return flow conduit 7a.

The shape and location of the ribs 61a and 61b is such that when the oil issues through the opening 52, the ribs oppose the flow of the oil across the surface 28a radially from the opening 52 with the result that the rotary means 5a is set into rotation, and thus the rotating body 5a together with the fluid-guiding ribs 61a and 61b provide an extremely efficient distribution of the cooling oil guaranteeing a very effective cooling of the piston 1a and preventing any undesirable deposits from being formed.

Referring to FIG. 3 in this embodiment the piston 111 also carries in its interior a support means 3b which supports, by way of a bearing 4b, a rotary means 5b provided with ribs substantially identical with those shown in FIG. 2 and cooperating in the same way with the inner surfaces of the piston 1b. The conduit means 2b supplies the oil under pressure which flows along the hollow tubular interior of the support means 315 and then through the hollow central portion of the rotary means 5b into the space between the transverse surfaces 25b and 28b of the piston and rotary means, so that the'oil under pressure will co-act with the fluid guide means formed by the ribs 61a and 61b, which in FIG. 3 have the same construction as indicated in FIG. 2. In this way the rotary means 5b will be set into rotation, and the oil will be efficiently distributed along the innersurfaces 25b and 26b of the piston 1b in the manner described above.

The embodiment of FIGS. 3 and 4 distinguishes primarily from that of FIG. 1 in that a'structure is provided to intensify the rotary movement of the rotary means 5b. In the illustrated embodiment this means for intensifying the rotation of the body 5b is formed by a turbine wheel 8 which receives the oil under pressure from the conduit means 212 and which is turned by the oil under pressure, this oil flowing into the space between the surfaces 25b and 28b only after it has passed through the turbine wheel. The arrangement of the turbine wheel with respect to the support means and the conduit means 2b, 7b is most clearly apparent from FIG. 4.

The turbine wheel 8 has a lower plate 84 fixed directly to an elongated shaft 81 which extends centrally from the plate 84 upwardly and coaxially along the interior of the support 3b and the rotary means 5b. The ribs 61a are fixed at their inner ends to the top end of the shaft 81 so that in this way the rotary means 5b is fixed to the turbine 8 for rotation therewith. This turbine 8 has an upper plate 85 formed with a central aperture through which the shaft 81 passes with sufficient clearance to provide for free flow of the oil from the central portion of the turbine wheel upwardly along the shaft 81 in the manner indicated in FIG. 3. The various blades 83 of the turbine wheel are arranged in such a way that the oil under pressure enters through the outer periphery of the wheel, causes the wheel to rotate, and of course the oil leaves through the central aperture of the upper plate 85 in the manner indicated in FIG. 3.

The support means 3b of FIG. 3 includes a tubular portion which surrounds shaft 81 with considerable clearance and which has at its top end the support for the bearing 4b. Within this tubular portion are arranged a pair of bearing rings 82 which surround the exterior surface of the shaft 81 to guide the latter and the turbine wheel for rotary movement. These bearing rings 82 are notched at their outer peripheral portions to permit for free flow of the oil upwardly through these rings to the space between the surfaces 25b and 28b. Of course after the oil flows downwardly along the surface 26b it will reach the return flow conduit 7b.

Thus, the embodiment of FIGS. 3 and 4 will achieve the results of the embodiment of FIG. 1, and, in addition, the turbine will provide for a more positive rotation of the rotary means 5b so as to further enhance the cooling action.

Referring nowto FIGS.'5 and 6, the embodiment of the invention illustrated therein also includes in the interior of the piston 1c.a suitable structure for very efficiently cooling the interior surfaces of the piston. Thus, it will be seen that the piston 1'c fixedly carries in its interior a support means 3c which is hollow so as to provide an interior space capable of communicating through the openings indicated in FIGS with the supply conduit 20 through which the oil under pressure is supplied. This oil flows upwardly along the tubular central portion of the support means 30 so as to reach the fluid guiding ribs of the rotary means 5c which is identical with that of FIG. 3 except that in this case the rotary means 50 has a downwardly extending central tubular portion 14 provided at its exterior with a spiral thread and surrounding the central tubular portion ofthe support means 30. Bearings 12- and 13 are situated between the tubular portions ofthe support means 3c and the rotary means 50 so as to support the latter for free rotation with respect to the support means 3c and the piston 10. Thus, with this embodiment the oil will flow along the interior of the support means 3c and into engagement with the fluid guiding ribs carried by the rotary means 50 to rotate the latter and .efficiently cool the inner surfaces of the piston in the manner described above in connection with FIGS. 1 and 3. The oil, after passing beyond the rotary means 50, will reach the return flow conduit 70.

With the embodiment of FIGS. 5 and 6, in order to intensify the rotation of the rotary means 5c 21 mass 15 surrounds the tubular portion 14 and has at its inner periphery-a spiral thread meshing with that of the tubular portion 14. This mass 15 is in the form of a flat annular body which at its outer periphery is formed with a pair of axially extending notches 24 which receive ribs 16 which are fixed to the piston 10, so that as a result while the annular mass 15 is capable of moving axially with respect to the piston in the interior thereof, nevertheless this mass 15 cannot rotate.

With this construction during reciprocation of the piston along its axis the mass 15 will be thrown first in one direction and then in an opposite direction. The tendency of the mass 15 to be thrown in either direction will cause the spiral threads to postively rotate the rotary mass 50, and it is to be noted that this rotary means 50 with the embodiment of FIGS. 5 and 6 will be ro tated first in one direction and then in an opposite direction so that an exceedingly eflicient distribution of the cooling oil is achieved with this construction.

The embodiment of FIG. 7 will achieve the results of the above embodiments with, however, a different structure for intensifying the rotation of the rotary means. Thus, it will be seen from FIG. 7 that the piston 1d fixedly carries in its interior the hollow support means 3d which communicates with the supply conduit 2d in the manner shown in FIG. 7, this support means 3d carrying the bearings 22 and 23 which fluid-tightly engage the exterior central tubular portion of the rotary means 5d of FIG. 7 so as to support the rotary means 'Sd for free rotary movement while at the same time the oil under pressure which reaches the interior of the hollow support mean 3d can flow from the hollow interior only into the hollow central tubular portion of the rotary means 5d through a suitable opening thereof in the manner indicated in FIG. 7. This oil under pressure will flow upwardly along the hollow central tubular portion of the rotary means 5d to engage the fluid-guiding ribs situated between the transverse surfaces 25d and 28d so that the oil will be distributed in the manner shown by the arrows to produce the desired cooling action, the oil then returning through the'return conduit 7d in the manner shown at the right portion of FIG. 7.

With the embodiment of FIG. 7, however, the rotary means 5d is positively rotated from the connecting rod 11. The connecting rod '11 will of course swing back and forth during reciprocation of the piston 1d, and. in accordance with the invention, as illustrated in FIG. 7, a motion transmitting means transmits the swinging movement of the connecting rod 11 to the rotary means 5d. This motion transmitting means includes a gear portion 9 which is fixed directly to the connecting rod 11 and which meshes with a toothed portion 10 fixed to the bottom closed end of the central tubular portion of the rotary means 5d. Of course the toothed portion 10 is spaced from the axis of the piston and the coinciding axis of the central tubular portion of the rotary means 5d, so that during swinging of the connecting rod 11 the motion transmitting means 9, 10 will oscillate the rotary means 5d first through one angle and then in an opposite direction back through the same angle, so that with this embodiment also the rotary means 5d will turn back and forth in order to provide an extremely efficient distribution of the cooling oil.

The manner in which the cooling oil is distributed by the fluid guide means *6 can be enhanced in a number of ways which are illustrated in FIGS. 817. In all of the structures shown in FIGS. 8-17 the piston 1 can be any of the above-described pistons and the rotary means 5 can be any of the above-described rotary means, while the fluid guide means 6 is also any one of the above-described fluid guide means of any of the above embodiments.

In the structure shown in FIGS. 8 and 9 a plurality of brush elements 17 are fixed to one or more of the fluid guiding ribs, and by wiping along the transverse surface 25 of the piston 1 these brush elements will provide a more intensive wiping action to enhance the cooling and cleaning of the surface 25 of the piston 1. Of course, the structure is shown on a greatly enlarged scale in FIGS. 8 and 9, it being understood that the gap between the upper free edges of the ribs 6 and the surface 25 is just enough for a film of oil, and the brush elements 17 of course form rather closely spaced bristles which provide an eflicient wiping and cleaning of the surface 25.

According to the embodiment shown in FIG. 10 the ribs of the fluid guide means 6 can be formed at their free edges with notches 18 which serve to increase the turbulence of the cooling oil and thus increase the cooling action in this Way.

With the embodiment of FIGS. 11 and 12 the fluid guide means takes the form of elements 19 divided into separate portions which at their free edges are curved first in one direction and then in an opposite direction in a manner similar to the teeth of a saw blade, so that with this construction also the turbulence of the cooling fluid is greatly enhanced.

Much the same results can be achieved with a structure as shown in FIGS. 13 and 14 where cross pins 20 are fixedly carried by the rib-s of the fluid. guide means 6, extending through these ribs adjacent their free edges so as to increase the turbulence of the cooling oil.

In the embodiment shown in FIG. 15 the rotary means 5 is provided between the ribs of the fluid guide means 6 with an undulating corrugated surface 90 having crests and depressions extending transversely across the spaces between the adjoining ribs of the fluid guide means 6, so that in this way these projections 90 form surfaces along which the oil will flow to be thrown substantially perpendicularly against the inner transverse surface of the piston 1 to provide an extremely effective cooling action.

Much the same results can be achieved with the construction of FIGS. 16 and 17 where a series of guide vanes 91 are distributed along the spaces between adjoining ribs of the fluid guide means 6, these vanes 91 extending transversely across these spaces and being curved in a manner shown most clearly in FIG. 16 so that the cooling oil will be thrown substantially perpendicularly by these guide vanes against the transverse inner surface of the piston 1 to provide an extremely effective cooling action.

Whre the piston has a particular area which is subjected to relatively high heat, it is possible to arrange elements such as the elements 90 and 91 at these locations to intensify the cooling action at selected localized parts of the piston.

With the structure of the invention the oil will flow very rapidly along the entire inner transverse surface of the piston as well as along the adjoining cylindrical surface thereof to provide an extremely effective cooling action. In addition, the rotation of the rotary means 5 will cause the fluid guide means 6 to cooperate with the inner surfaces of the piston to maintain these surfaces free of any deposits. Of course, where the swingingof the connecting rod is transmitted through a suitable transmission to the rotary means to turn the latter back and forth, it is not necessary to use the particular arrangement of FIG. 7 since any sort of crank and crank-pin drive will suffice for this purpose.

It is particularly to be noted that in all embodiments the rotary means 5 is supported for rotation in such a Way that it has a'certain limited amount of axial play so that during reciprocation of the piston it will be thrown through a very slight distance first in one direction along the axis of the piston and then in the other direction along the axis of the piston, to provide an increase and decrease, to a slight extent, in the spacing between the .fluid guiding means 6 and the inner transverse surface of the piston. In this way not only the wiping action of the ribs of the fluid guide means but also the turbulence of the cooling oil is enhanced.

It is to 'be noted that while with the structure of the invention prevention of carbon deposits are reliably avoided due to the intense cooling action achieved as a result of the speed and turbulence of the cooling fluid, so that a safe operation of the piston throughout all temperature ranges can be achieved, there is also an additional dvantage, since, due to the speed and turbulence of the cooling oil, it is not possible for the spaces between the ribs of the fluid guide means to become clogged, so that these spaces remain perfectly clean with the structure of the invention.

While the invention has been described above as applied to pistons driven from connecting rods which of course swing backand forth, it is to be understood that the invention is also applicable to pistons of the type used in crosshead engines where the pistons have piston rods fixed thereto and extending along the axes of the pistons. In such a construction the conduit means for delivering the cooling oil to and from the interior of the piston can be provided by way of suitable bores formed in the piston rod itself.

What is claimed is:

1. For use in an internal combustion engine, a hollow piston 'having an elongated hollow interior extending longitudinally along said piston and terminating at one end in an inner transverse surface from which a substantially cylindrical inner surface of said piston extends, support means carried by said hollow piston in theinterior thereof, rotary means mounted on said support means for free rotation with respect to said piston, said rotary means being situated between said support means and said inner transverse surface of said piston so that said rotary means is surrounded by said inner cylindrical surface of said piston, said rotary means having a transverse surface directed toward said transverse inner surface of said piston, fluid guide means carried by said transverse surface of said rotary means and situated between the latter and said transverse surface of said piston for guiding a cooling fluid, and conduit means situated in the interior of said piston and communicating with a space defined between said transverse surfaces for directing a cooling fluid to said guide means to be guided thereby for engagement with said transverse and cylindrical surfaces of said piston for cooling the latter.

2. The combination of claim 1 and whereinsaid support means is fixedly carried by and stationary with respect to said piston in the interior thereof, said rotary means is formed by a rotary body freely rotatable with respect to said support means, and said fluid guide means is formed by elongated fluid-guiding ribs projecting from said transverse surface of said rotary means toward said transverse inner surface of said piston.

3. The combination of claim 1 and wherein a turbine wheel is coaxially fixed to said rotary means for rotation therewith and is situated in the path of movement of the cooling fluid to said space between said transverse surfaces so as to be driven by the cooling fluid to induce rotary movement of said rotary means.

4. The combination of claim 1 and wherein said rotary means includes an elongated portion extending along the axis of said rotary means and having an exterior spiral thread, a mass surrounding said elongated portion and being formed wit-h a mating thread cooperating with said spiral thread, and guide means carried by said piston in the interior thereof and cooperating with said mass to guide the latter only for movement along the axis of said piston so that during reciprocation of said piston said mass will be thrown first in one direction along the piston axis and then in an opposite direction therealong so as to provide rotation of said rotarymass by way of said spiral threads.

5. The combination of claim 1 and wherein a connecting rod means is pivotally connected with said piston in the interior thereof and swings back and forth during reciprocation of said piston, and motion-transmitting means transmitting swinging movement of said'connecting rod means with respect to said piston to said rotary means for rotating the latter back and forth during swinging of said connecting rod means back and forth.

6. The combination of claim 1 and wherein said fluid guide means is in the form of a plurality of elongated fluid-guiding ribs projecting from said transverse surface of said rotary means and having distant from said latter transverse surface interruptions, and said ribs curving in opposed directions from one interruption to the next.

7. The combination of claim 1 and wherein said fluid guide means is formed by a plurality of elongated ribs which have distant from said transverse surface of said rotary means free edges which are notched at given intervals.

8. The combination of claim 1 and wherein said fluid guide means includes a plurality of ribs projecting from said transverse surface of said rotary means and a plurality of brush elements fixed to said ribs and also projecting toward said inner transverse surface of said piston to engage the latter surface during rotary movement of said rotary means.

9. The combination of claim 1 and wherein said fluid guide means includes a plurality of fluid-guiding ribs projecting from said transverse surface of said rotary means toward said transverse surface of said piston, and a plurality of pins projecting transversely through each of said ribs and distributed therealong for increasing the turbulence in the cooling fluid.

10. The combination of claim 1 and wherein said fluid guide means includes a plurality of ribs projecting from said transverse surface of said rotary means toward said transverse surface of said piston, said ribs being spaced from each other and extending substantially radially with respect to the axis of said piston, and said fluid guide means further including projections extending between said fluid-guiding ribs and distributed along the spaces therebetween.

11. The combination of claim 10 and wherein said projections are formed from the crest portions of corrugated surfaces respectively situated between pairs of adjoining fluid-guiding ribs.

12. The combination of claim 10 and wherein said projections are in the form of curved baifles which direct the cooling fluid substantially perpendicularly against said transverse inner surface of said piston.

References Cited by the Examiner UNITED STATES PATENTS 10/1915 Ver Planck 12341.35 8/1927 Sperry 1234l.l6 

1. FOR USE IN AN INTERNAL COMBUSTION ENGINE, A HOLLOW PISTON HAVING AN ELONGATED HOLLOW INTERIOR EXTENDING LONGITUDINALLY ALONG SAID PISTON AND TERMINATING AT ONE END IN AN INNER TRANSVERSE SURFACE FROM WHICH A SUBSTANTIALLY CYLINDRICAL INNER SURFACE OF SAID PISTON EXTENDS, SUPPORT MEANS CARRIED BY SAID HOLLOW PISTON IN THE INTERIOR THEREOF, ROTARY MEANS MOUNTED ON SAID SUPPORT MEANS FOR FREE ROTATION WITH RESPECT TO SAID PISTON, SAID ROTARY MEANS BEING SITUATED BETWEEN SAID SUPPORT MEANS AND SAID INNER TRANSVERSE SURFACE OF SAID PISTON SO THAT SAID ROTARY MEANS IS SURROUNDED BY SAID INNER CYLINDRICAL SURFACE OF SAID PISTON, SAID ROTARY MEANS HAVING A TRANSVERSE SURFACE DIRECTED TOWARD SAID TRANSVERSE INNER SURFACE OF SAID PISTON, FLUID GUIDE MEANS CARRIED BY SAID TRANSVERSE SURFACE OF SAID ROTARY MEANS AND 